My four top gun regrets include not buying an M17S, I instead bought an AR-15, i was then 18 and it was one of my first gun purchases. The M17s was brand new for 599 with 2 30 round mags. The AR was 675.

As for the gas piston kits. I have read that they cause excessive wear to the front/bottom of the buffer tube because the bolt carrier is being pushed backward from a different point causing it to ride slightly canted. I'm not sure they are a solution.

486,
Well, if the rifle stopped and could no longer work after the piston broke then I would agree, but it kept going. I call that reliable. Maybe not durable, but reliable.

I'd take durable over reliable, the reliability thing usually can be fixed easily [stuff like polishing rough edges, and cleaning up machining marks], the durability part is harder [you'd need new parts]...

Though I think the gas impingement system is very well thought out, it just isn't designed to run 4,000 rounds of ammo with no cleaning, it'll run fine so long as you do reasonable amounts of maintenance on it...

I agree with that, any system needs maintainance for longer life and reliability. And yes, I agree with the durable vs reliable thing too, was just saying that it kept running, that is why I went with a higher end piston system, I am a firm believer in you get what you paid for.

I agree with that, any system needs maintainance for longer life and reliability.

Is there any other reason the piston conversion exists other than making the amount of cleaning less? I've heard it detracts from accuracy, and even reliability in the cheaper designed systems [gouging your upper receiver with the bolt cam pin].

Sorry if it sounds like I'm trying to be an ass, it just comes naturally.

So far from my studying up on the pistons systems, yes the earlier version and still some now do gouge the inside of the upper and extension tube. That has been fixed by some manufactureres with a one piece bolt carrier with the rear end beefed up to tighten up the tolerances in the upper. That is what is in a HK416 from what I have been told, have not personally seen a BCG from a 416 but that is what most piston conversion manufacturers are doing to overcome the carrier tilt issue.
When Mac did his piece on the piston systems in Future Weapons shows, HK stated that the bolt was cooler which in turn helped with jams, in that they would not occur as often. They also point out, and I would be interested to see if a DI gun could do the same, is that the 416 could be fired at any angle and attitude; if that makes sense. Mainly that the platform no matter how it was in relation to the target could still fire without jamming.
Really, the piston does close the gap with DI SBR. That is really where it stands out.
I have seen the Over the Beach test that HK did in Germany, 416 vs M16. Seemed a bit staged to me, but I have seen other manufacturers videos of their systems being shot right out of the water, now that was impressive. Not that I will ever do such a thing but I thought I would like that kind of reliability. The idea is not new, as most of you probably already know, I think it was Stoner himself who tried to get the M16 changed over to a piston system many years ago.

So far from my studying up on the pistons systems, yes the earlier version and still some now do gouge the inside of the upper and extension tube. That has been fixed by some manufactureres with a one piece bolt carrier with the rear end beefed up to tighten up the tolerances in the upper. That is what is in a HK416 from what I have been told, have not personally seen a BCG from a 416 but that is what most piston conversion manufacturers are doing to overcome the carrier tilt issue.

The problem was also with the bolt cam pin bouncing back after the bolt clears the receiver lugs, gouging out the back of the cutout in the upper for the cam pin.

Mainly that the platform no matter how it was in relation to the target could still fire without jamming.

The real problem with feeding in all positions isn't cooler bolts, it's stuff like ejection, if you fire a gun that ejects real weak with the ejection port up it'll stovepipe, or a similar jam. With the AR it is pretty much a "look at what our gun can do that you don't know if yours can" type test...

I realize that alot of these tests posted are for the advertisement of the prospective system. And as we all know, everybodies new and improved is the best on the planet. LOL. I know that there have been things that have been improved upon that has brought the system into the 21st century and I am trying my system with what I think is the best user modified piston system on the market. I did not want one that I had to send my upper in or buy a brand name upper with one on it, I want to be able to take it on or off as I deemed necessary, and if it does not work, then I know I can write myself up my own little ad and sell the thing and go back to DI. Most people that I have heard who have good conversion are saying that they will never go back. Well I will try it out for myself and see.
As for the carrier tilt issue, I have heard both the rear bottom gouge and the one you mentioned. One piece bolts that have the modified rear end should take care of those problems.